Issue Resolving $ref in multi file spec

Swagger-codegen version

Codegen-Version : 2.4.0
Parser Version: 1.0.34

Description

In a multi file scenario where the file structure is as below:

|--- swagger.yaml
|--- responses /
|       |--- responses.yaml
|--- entities /
|       |--- common / 
|	|	|--- common.yaml	

If a response for a path in the swagger references responses/responses.yaml and the object structure here directly references a definition in common.yaml then the context of swagger.yaml must be used for addressing. Please note this is not specific to responses, i have reproduced consistently

If however the first reference is local then relative addressing behaves as per expected. Please see snippets below for further information

swagger.yaml

paths:
/pets:
  get:
     responses:
        '400':
          $ref: './responses/responses.yaml#/responses/invalidRequest'

responses.yaml

The below addressing only will work where as the expected addressing would be ../entities/common/common.yaml

responses:
  invalidRequest:
    description: The request was invalid
    schema:
      $ref: './entities/common/common.yaml#/definitions/errorModel'

If I change the above to the following it also works

responses:
  invalidRequest:
    description: The request was invalid
    schema:
      $ref: '#/definitions/errorModel'
definitions:
  errorModel:
      type: object
      $ref: '../entities/common/common.yaml#/definitions/errorModel'  

I have also observed that if the reference is an child object it needs to be relative to the initial calling file instead of the current file eg

definitions:
  testDefinition:
    type: object
    properties:
      propertyOne:
        type: string
        description: Test Property One
      propertyTwo:
        type: object
        description: Test Property Two.
        properties:
          propertyThree:
            type: array
            description: Test Property Three 
            items:
              $ref: './entities/common/common.yaml#/definitions/propertyThree'
            minItems: 1

Reproduce the reference resolution using swagger.yaml, responses/responses.yaml, and entities/common/common.yaml, including the nested propertyThree example. Compare resolution when the first reference is external with the local-reference workaround, and consider the issue done when nested $ref paths resolve relative to the file containing each reference without breaking the existing local case.